The invention relates to determining a power dependencies or relationships of a device connected to interconnected systems such as audio, video, or audio/video systems.
Determining the power type relationship of a unit or a subunit connected to a high speed serial bus such as an Institute of Electrical and Electronics Engineers (IEEE) 1394 standard serial bus, std 1394-1995, Standard For A High Performance Serial Bus, (Aug. 30, 1996) (hereinafter referred to as the xe2x80x9cIEEE 1394 standard serial busxe2x80x9d) is complex because of the many relationships that may exist between units and subunits or between subunits and other subunits. A power type relationship involves a single unit enclosing one or more subunits, and their corresponding power dependencies in which any single subunit may be powered on or off independently or dependently with the unit or other subunits in the unit.
One illustration of the problems associated with the conventional system relates to the IEEE 1394 standard serial bus that uses three general rules that are designed into an AV/C controller (xe2x80x9ccontrollerxe2x80x9d). One rule is if a unit""s power is activated, then the power to the subunit is activated. Another rule is that if a unit is deactivated, all the subunits of the unit are deactivated. Yet another rule is that if a subunit""s power is turned on or off, there is no effect on the unit or other subunits. These general rules do not support more complex situations. For example, whether a subunit is activated may depend upon whether other subunits in the unit are activated. In another situation, the power to a subunit may be completely independent of the unit or the subunit but depend upon whether a third subunit is activated. Given that the conventional system is unable to determine whether a unit is activated or deactivated in complex power type relationships, it is desirable to have a system and a method that is able to address complex rules associated with subunits and units.
The invention relates to determining the power type relationship that a unit has with its subunits, and a subunit has with its unit and other subunits within the unit. This is achieved by a first device such as a controller sending a POWER TYPE command to a second device or target device such as a unit or a subunit. A response frame, which is a part of the POWER TYPE command, is returned to the first device from the second device. The response frame provides the power type relationships that exist in the target device. Additional features, embodiments, and benefits will be evident in view of the figures and detailed description presented herein.